AMR and its relationship with human and animal morbidity is one of the biggest challenges facing modern medicine

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The problem of antimicrobial resistance (AMR) is very serious. According to reports, as many as 700,000 people worldwide have died from drug-resistant infections.

The overuse of antibiotics by humans, agriculture, and animal husbandry is still a key driver of the overall expansion of drug resistance.

There is considerable overlap in the types of antibiotics used in the human and veterinary sectors.

Antibiotics, such as preventive agents for disease prevention, back-up agents for controlling infections and promoting growth, are widely used in commercial poultry farms, pig farms, and aquaculture.

It is estimated that antibiotics can increase body weight by 56% and feed efficiency by 3-4%.

Therefore, they are a convenient choice for farmers, especially in countries where antibiotics are readily available without any restrictions.

Estimates of global consumption of agricultural antibiotics vary widely among countries. In low- and middle-income countries (LMIC) like India, these estimates are more guesswork than actual data due to the lack of active monitoring. Van Boeckel et al. (2015) estimated that global agricultural antibiotic consumption will increase by 67% from 2010 to 2030.

British economist Jim O'Neil (Jim O'Neil) found that 72% of studies show that human antimicrobial resistance is directly related to animal antibiotic consumption.

Long-term exposure to antibacterial drugs creates perfect conditions for cultivating drug resistance and increases the number of resistant bacteria, which significantly leads to an imbalance of the intestinal microbiota.

This is also the cause of antibiotic pollution in the environment, where 75-90% of antibiotics are excreted in unmetabolized form and then spread in the environment.

These antibiotics are not easily degraded due to their high water solubility and long half-life. Instead, they will persist in the environment for a long time. Therefore, animal manure is not only a source of resistant bacteria, but also contains active residues of antibiotics, which will further spread to water and soil.

Manure, if used as fertilizer for crops, can spread resistance in plants. Fat-soluble antibiotics, such as tetracycline and sulfonamides, accumulate in animal tissues over time.

There are a few examples of the spread of drug-resistant food-borne pathogens such as Campylobacter jejuni, Salmonella enterica, Typhimurium DT104, E. coli O157:H7, etc. in zoonotic diseases. Some of these examples include the emergence of ciprofloxacin-resistant Campylobacter after the introduction of fluoroquinolones, especially ciprofloxacin, which has been engaged in poultry production since 1995.

Other notable examples are the antibiotic avomycin, which promotes vancomycin resistance, and the vininicmycin, which has a similar effect to streptococcus. Cross-resistance (when a specific drug affects the resistance of bacteria and the susceptibility to other antibiotics) often occurs between the same class of antibiotics.

An example is the presence of extended-spectrum β-lactamase (ESBL), which leads to cross-resistance to penicillins and cephalosporins. The Enterobacteriaceae that produces ESBL is the main challenge for treatment.

The third and fourth generation cephalosporins Ceftiofur and Cefquinol are used as veterinary medicines to treat mastitis caused by Staphylococcus aureus, leading to the emergence of ESBL-E. coli. Ceftiofur is also used to prevent piglets to prevent arthritis, meningitis, sepsis and diarrhea.

ESBL enzymes exist on self-spreading plasmids, making the spread of these organisms between humans, animals, and the environmental sector more complicated. Drug resistance has developed to absolute drugs of last resort, such as carbapenems that use colistin.

Colistin is not a new drug. In fact, due to its nephrotoxicity, it was banned for human use in the 1970s. However, it is still used as a preventive and growth promoter for pigs. Klebsiella pneumoniae is an important human pathogen that can cause hospital-acquired and community-acquired infections, and resistance to colistin has emerged.

Resistance genes usually appear in clusters on mobile genetic elements such as transposons, plasmids, and integrons. Resistance genes to heavy metals and biocides are more common in nature, and they may select resistance genes together.

Resistance genes can be spread through a variety of bacterial species in different classifications. One of the most recent examples is the emergence of high resistance to the fluoroquinolone antibiotic ciprofloxacin in Kentucky, a non-typhoid Salmonella enterica serotype belonging to sequence type 198 (ST198).

Through whole-genome sequencing, it was found that S Kentucky ST198 was widely present in Indian poultry samples and showed considerable genetic correlation with Indian and international human isolates.

The Canadian Comprehensive Antimicrobial Resistance Surveillance Program (CIPARS) found that the voluntary withdrawal of ceftiofur antibiotics in hatcheries is associated with a reduction in human ceftriaxone-resistant Salmonella and E. coli infections. To reduce the spread of AMR, the European Union (EU) banned the use of antibiotics as growth promoters in agriculture in 2006.

Scandinavian countries such as Denmark, Norway, Sweden, and the Netherlands have set an example for the world by completely banning the use of antibiotics in the animal sector for the purpose of preventing and promoting growth.

Since bacteria are always present and there is no sterile natural meat, they tested another new strategy called "test and freeze" in Iceland, Norway and Denmark. In this case, poultry are tested before slaughter, and poultry tested positive for Campylobacter are frozen after slaughter to reduce the microbial load.

AMR and its relationship with human and animal morbidity is one of the biggest challenges facing modern medicine. The spread of zoonotic diseases is an area where the rate of emergence of drug-resistant species can be improved or reduced.

A comprehensive "one health" approach is needed to study the link between AMR and its spreading zoonotic diseases, using the most advanced sequencing technology.

Our world is changing rapidly. Due to extensive travel and meat import and export, it is more interconnected than before. Therefore, things that exist on the other side of the world will appear in our homes and on our plates in a few days. It's time to innovate new ways to curb the spread of AMR.

The author works at PGI in Chandigarh. The views expressed are the author’s own views and do not necessarily reflect down-to-earth views

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